diff between raw device and ufs in solaris

I just got in a client site to replace a dba for a short period of time(2-3 months), I find the datafiles are in ufs filesystem instead of raw devices
OS Solaris 2.6
Oracle 8.0.5
How much of a performance gain would I get by moving all the datafiles to a raw devices, assuming the db operations here quite a I/O intensive, the client cannot afford a big downtime, not really quite easy to justify to the client to buy more hardware due to some internal situations Is it worth the trouble?
Will a datafile created under ufs would work as expected if transferred to a raw device directly?

Your suggestion and comments would be greatly appreciated.

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